Quercetin as a novel activator of L‐type Ca²⁺channels in rat tail artery smooth muscle cells

Abstract

1 The aim of this study was to investigate the e ects of quercetin, a natural polyphenolic¯avonoid, on voltage-dependent Ca 2+ channels of smooth muscle cells freshly isolated from the rat tail artery, using either the conventional or the amphotericin B-perforated whole-cell patch-clamp method. 2 Quercetin increased L-type Ca 2+ current [I Ca(L) ] in a concentration-(pEC 50 =5.09+0.05) and voltage-dependent manner and shifted the maximum of the current-voltage relationship by 10 mV in the hyperpolarizing direction, without, however, modifying the threshold and the equilibrium potential for Ca 2+ . Quercetin-induced I Ca(L) stimulation was reversible upon wash-out. T-type Ca 2+ current was not a ected by quercetin. 3 Quercetin shifted the voltage dependence of the steady-state inactivation and activation curves to more negative potentials by about 5.5 and 7.5 mV respectively, in the mid-potential of the curves as well as increasing the slope of activation. Quercetin slowed both the activation and the deactivation kinetics of the I Ca(L) . The inactivation time course was also slowed but only at voltages higher than 10 mV. Moreover quercetin slowed the rate of recovery from inactivation. 4 These results prove quercetin to be a naturally-occurring L-type Ca 2+ channel activator.

Protective Effect of Quercetin against Gentamicin-Induced Nephrotoxicity in Rats

“…tea, red wine). 15) It has been reported that quercetin inhibited thrombocyte aggregation 16) and had an anti-hypertensive effect. 17) Interest in dietary phenolics has increased greatly recently, owing to their antioxidant properties (free radical scavenging and metal chelating) and their possible beneficial implications in human health, such as in the treatment and prevention of cancer and cardiovascular diseases.…”

Spasmolytic effect of Psidium guajava Linn. (Myrtaceae) leaf aqueous extract on rat isolated uterine horns

“…It has been reported that quercetin might be antagonizing the inward calcium membrane current, perhaps by blocking the L-type calcium membrane channels, leading to a decrease in smooth muscle contractile force (Lozoya et al, 1994). However, in another study, it has been reported that quercetin is an activator of L-type calcium channels (Saponara et al, 2002). These contradictory reports probably suggest that the spasmolytic activity of quercetin might be mediated via other mechanisms other than by antagonizing calcium membrane channels.…”

Octyl Gallate Inhibits ATP-induced Intracellular Calcium Increase in PC12 Cells by Inhibiting Multiple Pathways

“…Moreover, these compounds have been reported to be able to protect neuronal cells in various in vitro and in vivo models through different intracellular targets [8][9][10][11][12][13]. Phenolic compounds affect the function of voltage-gated ion channels [14][15][16][17] including voltage-gated Ca 2＋ channels [18]. Phenolic compounds have ability to affect agonist-induced [Ca 2＋ ]i increase in neuronal cells [19][20][21][22].…”